In producing a glass bottle, a crack such as crazing may be sometimes formed in a wall thickness of a bottle-mouth portion. This crack is referred to as a check. Glass bottles tend to have checks in limited regions of the bottle-mouth portions. Typically, there are a check generated in the top surface or near the top surface of the bottle mouth, a check generated in a screw thread portion of the bottle mouth, and a check generated in a skirt portion of the bottle mouth. Further, depending on the direction of the crack, the checks are classified into a vertical check extending in a vertical direction (substantially vertical direction) and a lateral check extending in a lateral direction (substantially horizontal direction).
Because the above-mentioned check can cause damage to the glass bottle, the presence or absence of a check is detected by imaging the bottle-mouth portion, and the glass bottle having the check is removed as a defective bottle.
Heretofore, there has been known a glass bottle inspection apparatus for automatically inspecting a glass bottle by imaging a bottle-mouth portion of a glass bottle to detect whether there is a check or not. The known glass bottle inspection apparatus has a single illuminating unit disposed above a bottle-mouth portion of a glass bottle and a number of (e.g., seven) cameras disposed around the bottle-mouth portion so as to surround the bottle-mouth portion. Scattered light emitted from the illuminating unit is applied to the bottle-mouth portion of the glass bottle, and if there is a check, the light is reflected by a crack plane of the check and is thus illuminated brightly. Therefore, images captured by the cameras include a brighter image area corresponding to the check than other image areas.